The present invention relates to vehicle power transmissions. More particularly, the invention relates to a power transmission uniquely adapted for use in motorcycles to enable reverse operation of the vehicle by means of power obtained from the starter motor.
Motorcycles are typically sufficiently light in weight that they can be readily maneuvered manually for slight movement, either forwardly or in reverse, as, for example, may be required in a garage or parking lot for parking purposes.
In these vehicles, therefore, since powered maneuvering has generally not been required, attempts have not been made to utilize either the mechanical or electrical power available on the vehicles for reverse operation, however slight.
More recently, however, with the significant increase in the size and weight of motorcycle-type vehicles it becomes desirable to provide such vehicles with the ability to move in reverse under power. Utilization of typical reverse gearing driven by the power unit of the vehicle is not conveniently available for this purpose, however, since the contemplated vehicle maneuvering is difficult to perform unless the speed of the vehicle when operating in reverse is slight. Consequently, any transmission of heretofore known-type used for such purpose would, of necessity, require a large reduction ratio and would, therefore, be unduly large in size and weight and too complicated in structure to effectively accomplish the desired result.
In Japanese Patent Application No. 60-238643 to the assignee herein there is described a device adapted to reverse a starter motor and to transmit the power to the output shaft after reducing the reverse revolution. This device has the convenience that it can reverse the vehicle by only operating a switch. On the other hand, however, use of the starter motor in this manner requires significant changes in the electric system of the starting device in order to rotate the starter motor output shaft forwardly or reversely. Further, because the reverse reduction device comprises a pinion and a gear, for slight reverse speed of the vehicle, the gear reduction system becomes considerably large in size and weight.
Compounding the problem is the fact that it is advantageous to rotate the starter motor at a high speed in respect to its output characteristic and consumption of electric power. When such motors are driven at high speeds, however, it is necessary to increase the reduction ratio of the starting system. For this reason it is necessary to provide a further reduction device whereby there is an inconvenience in that the size of the power unit must be increased.